German patent publication 4,011,929 discloses a motor-driven chain saw wherein the drive unit includes an internal combustion engine. The crankshaft of the engine carries a chain sprocket at one end of the crankcase for driving a saw chain which moves around a guide bar. Furthermore, the crankshaft drives a fan wheel which is held on a drive pin of the crankshaft on the opposite side of the crankcase within a fan housing. The crankcase of the engine is made of a metal material and is configured of two parts. The axis of the crankshaft lies in the partition plane of the crankcase parts which can be connected to each other. The crankcase is rigidly connected to the cylinder of the engine. The upper part of the crankcase is cast with the cylinder as one piece and is unified with the lower part of the crankcase holding the piston.
The housing of the known drive unit includes a connecting base having a recess in which the engine can be seated with the crankcase in advance from above and can be tightly clamped to a flange-like configured receptacle part of the connecting base. The connecting base for the engine is seated in the handle frame in the known motor-driven chain saw. The handle frame is made of plastic which has a low weight while having high strength and excellent vibration damping characteristics. The total weight of the portable handheld work apparatus to be carried by the operator is intended to be low with respect to the best possible manipulability. The connecting base for accommodating the engine is used in the known motor-driven chain saw in order to facilitate assembly. The connecting base imparts the required stiffness to the force loaded total assembly; however, the component as an additional part increases the weight and the manufacturing costs.